Field of the Invention
The present invention relates to Stirling cycle systems, and more particularly to a new and improved Free-Piston Stirling cycle system (such as a Stirling cycle engine) of the relative gas spring type especially adapted for operation at frequencies of 50 Hz. and above. In all practical relative gas spring configuration Free-Piston Stirling systems of which I am aware, (that is, systems wherein the force required to impart motion to the displacer is generated by the relative motion between the displacer and the power piston) the ratio of the diameter of the gas spring piston to the diameter of the displacer is not more than about 0.30, and all such systems are limited to operation of no greater than 30 Hz.
I have discovered that high frequency operation (50 Hz. and above) can be achieved in a mechanically simple, relative gas spring configuration Free-Piston Stirling system by making the ratio of the diameter of the gas spring piston to the diameter of the displacer at least 0.50. Accordingly, it is to be understood that the present invention is applicable to a wide range of designs of relative gas spring Free-Piston Stirling systems, since the important and novel aspects of this present invention lie in the arrangement and construction of such a relative gas spring configuration Free-Piston Stirling system wherein the ratio of the diameter of the gas spring piston to the diameter of the displacer is made to be at least 0.50. The invention is especially useful in the "nested" design of Stirling System, such as that shown and described, for example, in patent application Ser. No. 484,216, Filed Feb. 23, 1990 (1242-105/MTI 10-D-335) entitled "Stirling Free Piston Cryocooler", assigned to the same assignee as this present invention, and which description is incorporated herein by reference.